Our previous work showed that many lichenized Ascomycetes can generate hydroxyl radicals using quinone-based extracellular redox cycling. During cycling, hydroquinones must be formed and subsequently regenerated from quinones using a quinone reductase (QR). However, we also showed that no simple correlation exists between QR activity and rates of hydroxyl radical formation. To further investigate the role of QR in hydroxyl radical formation, three model lichen species, Leptogium furfuraceum, Lasallia pustulata and Peltigera membranacea were selected for further investigation. All possessed QR activity and could metabolize quinones, and both Leptogium furfuraceum and Lasallia pustulata actively produced hydroxyl radicals. By contrast, P. membranacea produced almost no hydroxyl radicals, and although the lichen readily metabolized quinones, no hydroquinone production was detected. Peltigera had laccase (LAC) activity that was c. 50 times higher than in the other two species, suggesting that LAC rapidly oxidizes the hydroquinones, preventing radical formation deriving from auto-oxidation. It appears that in some lichens hydroxyl radical formation is blocked by the presence of high redox enzyme activity. QR from P. didactyla was studied further and found to display similar properties to the enzyme from free-living fungi, although it possessed an unusually high molecular mass (c. 62 kDa).

我们之前的工作表明，许多地衣化子囊菌可以使用基于醌的细胞外氧化还原循环产生羟基自由基。在循环过程中，必须形成对苯二酚，然后使用醌还原酶 (QR) 从醌中再生。然而，我们还表明，QR 活性与羟基自由基形成率之间不存在简单的相关性。为了进一步研究 QR 在羟基自由基形成中的作用，选择了三种模型地衣物种，即 Leptogium furfuraceum、  Lasallia pustulata 和 Peltigera membranacea 进行进一步研究。都具有 QR 活性并可以代谢醌类，以及 Leptogium furfuraceum 和 Lasallia pustulata 积极产生羟基自由基。相比之下，  P. membranacea 几乎不产生羟基自由基，虽然地衣很容易代谢醌，但没有检测到对苯二酚的产生。 Peltigera 的 漆酶 (LAC) 活性为 c。比其他两个物种高 50 倍，表明 LAC 迅速氧化对苯二酚，防止自氧化引起的自由基形成。似乎在一些地衣中羟基自由基的形成被高氧化还原酶活性的存在所阻止。 进一步研究了来自P. didactyla 的QR  ，发现它显示出与来自自由生活真菌的酶相似的特性，尽管它具有异常高的分子量 ( c . 62 kDa)。